For the purpose of more efficiently using energy of wood biomass, carbonizing treatment of the wood biomass is performed in an attempt to improve a heating value. As the carbonizing treatment of the wood biomass, for example a method of indirectly heating the wood biomass under a low oxygen atmosphere at a high temperature of 300° C. to 700° C. using a pyrolysis furnace such as an external heat type pyrolytic gasification furnace is known. According to this method, a carbonized product with an improved heating value can be produced.
As a method of producing the carbonized product, high-temperature carbonization in which wood biomass is indirectly heated at a high temperature of 500° C. to 700° C., and half carbonization (torrefaction) in which wood biomass is indirectly heated at 300° C. or so are known. In the high-temperature carbonization, a carbonized product in which a high gasification rate and spontaneous exothermicity are suppressed can be produced by securing a sufficient treatment time at a predetermined temperature. In the half carbonization, a carbonized product with both crushability and a residual ratio of heat quantity can be produced by controlling a temperature range to be very narrow see Patent Document 1).